Pete Barnes, a veteran pilot with more than 25 years' experience, could have veered off route and missed a turning on the River Thames as he tried to radio Battersea heliport to say he wanted to make an unscheduled landing because of the fog, the Daily Telegraph said.

Aviation lawyer and qualified pilot James Healy-Pratt told the newspaper: "It could have taken 10 to 15 seconds to make the change of radio frequency, in which time the helicopter could have flown up to half a mile."

Air accident investigators are likely to focus on trying to account for a "missing minute", during which Mr Barnes was out of contact with flight controllers, the Telegraph said.

Mr Barnes, 50, from Berkshire, died when the AgustaWestland 109 he was piloting crashed into a crane at the side of The Tower at St George Wharf at 8am on Wednesday, just yards from Vauxhall Station.

His helicopter plunged to the ground 700ft below, killing Matthew Wood, 39, from Sutton, south London as he walked to work.

Mr Barnes had been flying from Redhill in Surrey to Elstree, Hertfordshire, but he asked to be diverted to Battersea heliport because of bad weather.

David Learmount, from aviation website Flightglobal, told the Independent that a small change in weather conditions, which are thought to have worsened at about the time of the accident, could have been enough to "trap" Mr Barnes.

"Weather will turn out to be the key issue (in the investigation). When you fly in marginal conditions, it only needs a little dip in what you were expecting and you're pretty much trapped," Mr Learmount said.

"He probably did not see the crane until it was too late. Sometimes even bright lights are difficult to see in foggy conditions."

Work to make the scene safe and remove the crane continued today.

A spokesman for Brookfield Multiplex, the building contractor at The Tower, said the crane wreckage will be removed in two stages.

Small loose parts of the crane were removed or secured yesterday, and today work to erect a 600-tonne mobile crane at the site will take place, weather permitting.

Work on removing and replacing the damaged sections of the crane will start tomorrow, and the company hopes to finish the process by the middle of next week.

The crane is not at risk of collapse and has been examined by the Health and Safety Executive and Lambeth Council, the company said.

Transport for London (TfL) said a number of roads would be shut for "several days" while work is carried out.

Drivers are advised to avoid the Vauxhall Cross and Kennington Park areas today and over the weekend.

Motorists who have to enter the congestion charge zone as a result of diversions will not have to pay the toll while using signed routes.

Leon Daniels from TfL said: "Our staff continue to work and minimise disruption to people travelling through the Vauxhall area following the terrible incident and are assisting the emergency services where necessary.

"Due to the ongoing road closures and diversions, traffic in the area has been very busy.

"We are therefore strongly advising road users to avoid the area and use alternative routes throughout Friday and across the weekend."